Multiple-input/multiple-output (MIMO) technology, that typically utilizes multiple antennas, is currently being investigated, developed and standardized in order to increase data rates as well as to improve the radio link quality. Examples of various MIMO techniques may be found in the Institute of Electrical and Electronics Engineers (IEEE) 802.11n draft standard and in the third generation partnership project (3GPP) long term evolution (LTE) standards body. The global system for mobile communication enhanced data rates for global evolution radio access network (GERAN) is also investigating the use of multi-antenna mobile stations (MS) for the purpose of reception diversity.
A challenge exists, however, in the development of MIMO systems due to the difficulty of implementing multiple antennas in a small sized WTRU, such as a cell phone, personal data assistant (PDA), or other wireless device. Due to the smaller size of many WTRUs, the size, spacing and number of antennas that can be implemented in them is limited. Additionally, implementing multiple antennas may also affect the aesthetics of the device.
It would therefore be beneficial to provide an external antenna and radio frequency unit for use with a WTRU that would overcome the limitations described above.